Speech interfaces have become important features in mobile devices today. Some devices have the capability to respond to speech even when the device's display is off and in some form of low power mode and potentially at some distance from the user. These requirements place significant demands on system design and performance including the need to keep the microphone in an “always listening” mode.
In other examples, the device keeps only parts of the signal chain powered up, e.g. the microphone and a digital signal processor (DSP) or central processing unit (CPU), with an algorithm for detecting a “voice trigger.” Upon recognizing a voice trigger, the rest of the system is powered up from its sleep mode to perform the desired computational task.
The above-mentioned previous approaches suffer from several disadvantages. For example, these approaches tend to utilize or waste much power. This waste of power reduces the battery life of such systems. In other examples, the system may suffer from performance issues. These and other disadvantages have resulted in some user dissatisfaction with these previous approaches.
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